Implement a command line interface to show custom OSD

[mkozjak]

Summary by Sourcery

Add a configurable on-screen volume HUD position and a command-line entry point to trigger it.

New Features:

• Introduce a CLI target that displays the Tahoe volume HUD based on command-line options for volume, title, and screen position.
• Add a HUDPosition enum and API support to place the HUD in one of nine screen locations when not anchored to a status bar item.

Enhancements:

• Allow TahoeVolumeHUD to optionally hide the app icon and reflow the title when no player icon is provided.
• Adjust HUD positioning constants and glass tint to better align the HUD with screen edges and provide a fully transparent background on supported macOS versions.

This is proof-of-concept idea and is vibe-coded.

Build:

xcodebuild -project "Volume Control.xcodeproj" \
           -target "volume-control-osd" \
           -configuration Debug \
           CODE_SIGNING_ALLOWED=NO

Run:

./build/Debug/volume-control-osd.app/Contents/MacOS/volume-control-osd --title Bluesound --volume 30 --position top-right

References #48.